Undesirable nuisance plant growth such as algae, bacteria, mold and fungus, have been a common problem for surfaces adjacent to freshwater and seawater areas. For example, swimming pools, fountains and other manmade vessels that hold water are subject to fouling by algae.
Past methods for preventing algae type plants have had numerous problems. Usual current surfacing agents for treating algae growth are generally toxins that can also be toxic to humans above threshold concentrations. For example, tributyl tin and cuprous oxide have been shown to be effective toxins and have been incorporated into marine paints for the hulls of boats. While the gradual release of toxins when the boat is underway can be acceptable, a boat in port can generate unacceptable concentrations of toxin.
Titanium Dioxide has been known to be used in commercial paint formulations and can be generally bright white in color. See for example, U.S. Pat. No. 5,142,058. However, these preparations are made deliberately so as to be photo-inactive where any form of photo-activity is regarded as a negative characteristic, because the organic binder containing the pigment can be ultimately attacked and destroyed.
A standard toxin agent is chlorine. Chlorine is a standard means for disinfecting both swimming pool water and drinking water. However, disinfectants such as chlorine become spent and must be replaced over time with repetitive additional costs. Heavy chlorination of microorganism containing water can also result in suspected carcinogenic by-products such as trihalomethanes.
Toxin release agents are not only inferior due to their health effects on higher order plants and animals, but also because they represent a consumable item that must be eventually replaced.
Many types of algaecides function as light blockers, absorbing the light necessary for algae growth. This involves dissolving one or more dyes in the water whose net absorption spectrum matches that of the algae. Thus, the water is dyed with an unnatural shade of blue or green that can be aesthetically unappealing. These algaecides are also subject to eventual decomposition and require periodic replenishment.
The subject inventor is aware of photocatalysts being used for the decomposition of organics. See U.S. Patents: U.S. Pat. No. 4,863,608 to Kawai; U.S. Pat. No. 5,244,811 to Matthews; U.S. Pat. No. 5,332,508 to Foster; U.S. Pat. No. 5,501,801 to Zhang; U.S. Pat. No. 5,541,096 to Nomura; U.S. Pat. No. 5,547,823 to Murasawa; U.S. Pat. No. 5,593,737 to Meinzer et al.; U.S. Pat. No. 5,616,532 to Heller et al. However, none of these photocatalysts use algae inhibiting co-catalysts to increase the decomposition of algae.
The subject inventor and assignee are also the same inventor and assignee of both U.S. Patents U.S. Pat. No. 5,518,992 entitled: Photocatalytic Surfacing Agents For Inhibiting Algae Growth and U.S. Pat. No. 5,880,067 Photocatalytic Surfacing Agents With Varying Oxides For Inhibiting Algae Growth, to the same inventor and same assignee as this invention. The ""992 patent specifically deals with using platinum(Pt) as a co-catalyst for photocatalytic agents such as TiO2 (titanium dioxide) and WO3 (tungsten oxide). While, platinum is an excellent co-catalyst it is also a very expensive material costing for example $400/oz. Thus even though the co-catalyst is present at only a 1.0% by weight loading, at $400.00 per ounce, even as a bulk commodity, the Pt would comprise 98% of the cost of the photocatalyst. Previous work has shown that the minimum coverage of photocatalyst to achieve an optimized photo effect across a surface is about 1.0 mg/cm2. Pure Anatase TiO2 costs about $1.00/lb. Therefore, the photocatalyst cost to cover 100 m2 with plain TiO2 would only be $2.20. On the other hand, if the TiO2 were to be modified with 1.0% by weight of Pt, the cost of the photocatalyst would rise to $141.00. Clearly there is strong motivation to find a less expensive yet effective, co-catalyst.
The first objective of the present invention is to provide photocatalysts with co-catalysts as surfacing agents for inhibiting nuisance organisms such as algae, bacteria, mold and fungus.
The second object of this invention is to provide photocatalysts with co-catalysts as surfacing agents for inhibiting nuisance organisms that are nontoxic.
The third object of this invention is to provide photocatalysts with co-catalysts as surfacing agents for inhibiting nuisance organisms that becomes active and remains active when light is applied.
The fourth object of this invention is to provide photocatalysts with co-catalysts as surfacing agents for inhibiting nuisance organisms that becomes active and remains active when light is applied.
The fifth object of this invention is to provide photocatalysts with co-catalysts as surfacing agents for inhibiting nuisance organisms that does not need constant replacement nor replenishment to remain active.
The sixth object of this invention is to provide photocatalysts with co-catalysts as surfacing agents for inhibiting nuisance organisms without coloring water with algacidal dyes.
The seventh object of this invention is to provide photocatalysts with co-catalysts as surfacing agents for inhibiting nuisance organisms that has a one-time economical cost.
Embodiments of the invention include mixing a catalyst of titanium dioxide or tungsten oxide with carbon, Co2P, Co, Ni, Fe, and Cu.
Further objects and advantages of this invention will be apparent from the following detailed description of a presently preferred embodiment which is illustrated schematically in the accompanying drawings.